Gut microbiome dysbiosis in traumatic brain injury: Implications for neurological recovery and microbiome-targeted interventions

Abstract

Traumatic brain injury (TBI) is a major cause of mortality and long-term neurological disability worldwide. In addition to primary brain damage, TBI induces complex secondary pathophysiological responses involving neuroinflammation, systemic immune dysregulation, gastrointestinal dysfunction, and alterations in the microbiota–gut–brain axis. Increasing attention has therefore been directed toward the role of gut microbiome dysbiosis in the progression of secondary brain injury and its potential as a therapeutic target. This narrative review aimed to synthesize current evidence regarding the relationship between TBI and disruption of the microbiota–gut–brain axis, with particular emphasis on the mechanisms underlying gut microbiome dysbiosis and its contribution to secondary brain injury. The review discusses neuroinflammatory responses, alterations in intestinal barrier integrity, enteric and autonomic nervous system involvement, vagal signaling, and microbiota-derived pathways implicated in brain–gut communication after TBI. In addition, the therapeutic rationale, available evidence, translational considerations, and current limitations of microbiome-targeted approaches, particularly probiotics and fecal microbiota transplantation, are critically discussed. This review provides an updated framework for understanding the microbiota–gut–brain axis in TBI and identifies areas requiring further mechanistic and clinical investigation.